Background: Clinical trials have demonstrated that pharmacotherapies can safely treat attention-deficit/hyperactivity disorder (ADHD) in adulthood. Eligibility criteria in these trials may significantly limit their external validity by excluding a significant portion of adults with ADHD in the general population. In particular, exclusion criteria may frequently exclude individuals with comorbid mental health conditions, which are common in the adult ADHD population.

Results: Adults with ADHD in the community sample had higher rates of lifetime psychiatric comorbidity, lower GAF scores, and lower occupational codes than those in the clinical trial. The clinical trial eligibility criteria would have excluded 61% of community sample adults with ADHD. This excluded portion of the community sample had higher rates of lifetime psychiatric comorbidity and lower GAF scores than clinical trial participants.

Conclusions: Adults with ADHD participating in the clinical trial had less evidence of functional impairment and endorsed less psychiatric comorbidity than the majority of community sample subjects with ADHD. This suggests that findings from clinical trials may have limited external validity for adults with ADHD in the general population, particularly for those adults with ADHD with the greatest burden of comorbid psychopathology.